This invention relates to the etching of aluminum foil for electrolytic capacitors, and in particular to a process utilizing alternating current and a chloride etchant bath containing phosphate and chromate ions.
AC etching of aluminum for lithographic plates, electrolytic capacitors, and other articles is known. Similarly, chloride etchants containing chromate and phosphate for use with DC current are known. The latter have produced porous anode elements.
A copending application filed on even date with this application teaches the advantages of using a phosphate in the etchant solution.